Letters

Deck Details

To the Editor:

The article
"Building Better
Decks" (6/03) was very informative. We too work in the
north Virginia area, although we probably only do 12 to 24
decks, screen porches, and patios a year, along with kitchens,
bathrooms, basements, and small additions. I agree with much of
what Jim Craig writes, especially his main message, that
quality options, materials, and workmanship command higher
prices and create happier customers. I thought some of his
details were very good.

However, one picture struck me as incorrect based on what I
have read about Trex from the manufacturer. The cover photo
shows two men slamming a Trex deck board into place. The
picture leads me to believe that the space for the board is so
tight that they have to wedge it into place.

If you have worked with Trex, you know the material
characteristics allow for this to happen (the boards can be
manipulated in various ways), but everything I have read from
the manufacturer states that you must leave substantial room
for expansion, including at the ends of the boards. Here you
have ends butting to the side of a Trex board apparently so
tight the crew has to force it into place. We generally use a
3/16-inch to 1/4-inch space between all Trex boards.

Tom McMurray, Owner

McMurray Builders

Lorton, Va.

Jim Craig responds: Your concerns about the expansion of
Trex in relationship to the spline board being forced into
place are valid. In this case, the air temperature had reached
85°F and hotter, so we knew the Trex boards had probably
reached their full expansion. We cautiously gave aesthetics
precedence: If we had left a gap along both sides of our 2x6
spline board, the gap would have grown and become caked with
organic debris from the trees overhead. On page 58 of the
article, you can see how we continuously block beneath both
edges of the 2x6 spline board. Unfortunately, that also allows
organic debris to collect in this location if the gap is too
big. Our experience with this tight-fitting installation on hot
(85°F plus) days has been very favorable. We are
currently building about 90 Trex decks a year.

Defending Gable Vents

To the Editor:

I just read the Q&A
"Can You Combine Ridge
and Gable Vents?" (6/03) and couldn't believe the advice.
There were no details on the size of the gable vents, the
length of the ridge, or the geometry of the house, which
undoubtedly change performance. However, if you have spent any
time in attics, I think you will agree that most ridge vents do
not provide for much air flow. The tiny gable vents shown in
the diagram surely won't provide much either, but an adequately
sized set will out-ventilate ridge vents in most
situations.

I also doubt that the air will stagnate as profoundly as
described. In most cases, the breeze will deflect off of the
framing in the attic, creating eddies that cause the air to
mix. As far as pulling rain and snow in through ridge vents,
most have small enough holes that it would not be
significant.

I have held the back of my hand up to the inlet into ridge
vents in many attics and have yet to feel any air movement. The
temperatures in any attic that relied on eaves and ridge vents
have always been higher than ones with adequate gable vents.
Although attic physics is complex, I believe that most attics
would be better served by leaving the gable vents open.

Wayne Appleyard

Architect

Ann Arbor, Mich.

Mike Keogh responds: Your letter assumes that I condemn
gable vents in favor of ridge vents. In fact, I promote the use
of gable vents provided they are sized and placed correctly and
are complemented by "field" or "pot" vents to optimize
performance of the venting system.
The undimensioned diagram in the article illustrated a simple
rectangular building with full ridge and two gables and assumed
vents would be sized to the minimum area required by code. You
are correct in stating that the geometry of the house affects
performance. However, only if the gable-width-to-ridge-length
ratio did not allow for installing sufficient ridge vent
capacity would I opt for gable vents supplemented by field
vents. Adequately sized gable vents, even with continuous
soffit venting, cannot match performance of the same roof with
a good ridge vent replacing the gable vents. Ideally, air
should flow over the entire underside of the roof deck,
collecting solar heat and venting it to the atmosphere. The
ridge-soffit combination is undoubtedly the most effective way
to achieve that.
There are many ridge vents to choose from, and, despite
manufacturers' claims, all are not equal. When assessing
airflow performance of different vents, some might say, as with
beer, "There is no such thing as a bad one, just some better
than others." Unfortunately, that is not entirely true, and I
have, on several occasions, removed the vent "filter" material
to increase air flow, thus curing a performance problem with no
adverse effects later. The architect or reroofer must assess
available products, make a sensible choice, and ensure that
they are correctly installed.
My own observations of dry powder snow as well as attic smoke
tests have confirmed University of Illinois research that
proved this phenomenon. Incidentally, a surprising amount of
dry powder snow can penetrate relatively small vent mesh
(smaller than 1/8 inch). It is typically only noticed later
when it melts and stains the ceilings below. (Often vapor
barriers keep moisture away from the drywall, but saturated
insulation has no R-value and can trigger attic mold and
rot.)
Checking air flow with the back of your hand can be misleading
because in well-designed systems, the volume of air exhausting
is distributed over the entire ridge, reducing velocity at any
one spot. Also, summer temperatures in the attic will generally
be above blood temperature, and so the stream is less
detectable. Of course, poor flow may indicate insufficient or
blocked intake at the eaves, blockage of exhaust vent filter
media, or incorrect installation.

Reader Wants Balance

To the Editor:

I would like to respond to the article on improving safety
standards for hot water heaters
(In the News,
6/03). It is to be desired and encouraged that all of us in the
industry work to improve safety. Improving the safety of hot
water heaters is no exception. My suggestion is that the
article lacks an opposing balance.

The unpleasant subtheme of this article is that irresponsible
behavior leads to tragic results; innocent third parties often
suffer. Storage of gasoline in or around a hot water heater is
irresponsible behavior. Every example cited in the article is
of negligent human behavior causing a tragedy.

Viewed from a broader perspective, the article actually
documents the admirable safety of current standards. Water
heaters are not defective. Of the hundreds of thousands,
perhaps millions, of water heaters in use at this time, there
are only 2,000 fires, only 300 injuries, and only 19 deaths
annually. Statistically speaking, one probably has a greater
chance of winning the lottery than of dying in a water heater
accident. The sad fact is that most of these tragedies were
easily preventable.

It should not be assumed that a higher standard would save
lives.... Up to a point, improving water heaters only
encourages people to be even more negligent. People will come
to believe that they are not dangerous at all, resulting in
even more accidents.

We should treat new systems with caution if not skepticism. We
have good intentions in improving hot water heaters, but we
should be very circumspect about the results. My challenge to
JLC is to provide clear, balanced, factual articles.

Greg Casorso

Casorso Construction

Orinda, Calif.

Screening Chimney Pots

To the Editor:

Your item on chimney pots
(Products: On the
Job, 6/03) recommends screening the top with 1/2-inch wire
mesh. Screening is a great idea for keeping birds and animals
out of a chimney, but it should be noted for safety's sake that
the net-free area of the 1/2-inch mesh screen must not be less
than four times the area of the outlet of the chimney flue it
serves. Screening flat across the top of the pot can cause
blockage and result in carbon monoxide backing up into the
residence. Typically, the screen should be built with four
sides and a top for a rectangular flue; for a round chimney
pot, the screen could go around the circumference of the
opening and rise with a round screen cap on top.
Stainless-steel wire works well to "sew" the pieces
together.

The larger screen area may not be as pleasant to the eye, but
safety should be the number one concern.